The present invention relates to radio frequency identification (“RFID”) technology. More specifically, it relates to the RFID tags that are used on each product or set of products to uniquely identify such product or products.
Bar codes containing a Universal Product Code (“UPC”) have become a nearly ubiquitous feature of modern life. The vast majority of products, as well as packages, containers and other elements in the stream of commerce now bear a bar code to allow for convenient tracking and inventory control.
However, bar codes have some drawbacks. Bar codes are “read only,” in that they are merely a printed set of machine-readable parallel bars that cannot be updated. Bar codes cannot transmit information, but instead must be read by a scanner. Bar codes must be scanned within a relatively short distance and must be properly oriented for the bar code to be read.
“Smart labels,” generally implemented by RFID tags, have been developed in an effort to address the shortcomings of bar codes and add greater functionality. RFID tags have been used to keep track of items such as airline baggage, items of clothing in a retail environment, cows and highway tolls. As shown in FIG. 1, an RFID tag 100 includes surface area 105 and antenna 110. In this example, RFID tag 100 is activated by a magnetic field 145 generated by an RFID reader 125. The tag's antenna 110 picks up the magnetic signal 145. Conventional RFID tags are passive and are generally configured with a particular surface area for reflecting back the magnetic signal at a particular modulation. That is, RFID tag 100 modulates the signal 145 according to information coded in surface area 105 and reflects the modulated signal 155 back to the RFID reader 125.
RFID tags use the Electronic Product Code (“EPC” or “ePC”) format for encoding information. An EPC code includes variable length bits of information (common formats are 64, 96 and 128 bits), which allows for identification of individual products as well as associated information. As shown in FIG. 1, EPC 120 includes header 130, EPC Manager field 140, Object class field 150 and serial number field 160. EPC Manager field 140 contains manufacturer information. Object class field 150 includes a product's stock-keeping unit (“SKU”) number. Serial number field 160 is a 40-bit field that can uniquely identify the specific instance of an individual product i.e., not just a make or model, but also down to a specific “serial number” of a make and model.
In general, existing RFID tags are passive filters that represent a sequence of numbers based on the frequencies they reflect. Said in another way, each item's RFID tag bounces back a certain frequency that corresponds to the item's identification. Conventional RFID tags have specific patterned surface areas that are designed to reflect specific frequency ranges. Thus, when a reader sweeps within a plurality of different frequency ranges, the reader will receive a reflected signal when a particular RFID tag matches one of the frequency ranges. The obtained reflected signal's particular frequency modulation then corresponds to particular information, such as serial and model number, for a particular RFID tag.
Although conventional RFID tags work well in particular applications, the RFID information of each tag is static and cannot change over time. Thus, any parameter of the corresponding product (such as operational status) cannot be dynamically included in the conventional passive RFID tag.
In view of the above, there is a need for improved RFID tags that dynamically specify changing information, such as operational status, regarding its associated product. Additionally, there is a need for mechanisms for reading and managing dynamic RFID tags.